Rail chiefs in the Republic of Ireland are seeking permission to lodge a €2.5b proposal to develop an underground segment to Dublin light commuter rail system, the Dart.

An application –lodged yesterday with the city’s planning authority– sets out the details for the plan which will include boring 7.6km worth of twin-tunnels through the city’s centre.

It’s thought that the scheme could treble the number of rail passengers in Dublin.

The scheme would connect the Northern and Kildare lines, currently not linked, and would also involve the construction of brand new underground stations at Spencer Dock, Pearse Station, St Stephen's Green, Christchurch and Heuston Station.

The scheme would involve a collaboration between private industry and public money, but the Transport Minister refused to disclose to journalists just how much public money would be put in to the venture.

It’s believed that the Government will move to ask the European Investment Bank for money towards some aspects of the project.

The scheme – called the Dart Underground– will finally link all of the capital's rail systems - Dart, Commuter, InterCity, Luas and Metro and form for the first time a fully integrated rail network, something which the city’s residents have been clamoring for for years.

And Ianrod Eireann, Ireland’s national rail company, said that it believes that the system could treble rail traffic as more Dubliners see taking the rail as a viable and effective transport option.

Up to 7,000 jobs would be created during construction, according to plans.

Artist's impression of the proposed underground system